This invention relates to a movable laser beam machining head used with a three-dimensional laser beam machine, etc.
FIG. 4 is a sectional view to show a laser beam machining head in a related art shown in JP-A-7-178546, etc., for example. In FIG. 4, laser light L emitted from a laser oscillator (not shown) passes through an optical path 6 and is incident on a torch main unit 1 forming a machining head section and then is emitted through a hole of a nozzle section 7 for machining a workpiece (not shown) to be worked on.
It has a flange 4 forming a part of the torch main unit 1 and comprising a magnet 8, a switch 5, and a through hole 10 at predetermined positions and a bracket 2 having a groove 3 being formed corresponding to the shape of the flange 4 and comprising an inner wall 3a and inner bottom 3b and comprising a magnetic substance 9 and a screw 11 and an elastic member 12 corresponding to the magnet 8 and the through hole 10 and the flange 4 is fitted into the groove 3 and they are joined by the magnetic force of the magnet 8 and the magnetic substance 9, whereby the bracket 2 holds the torch main unit 1.
In the described structure, if some obstacle, for example, a workpiece collides with a tip nozzle part 7, etc., at the tip of the torch main unit 1 and an impulsive force exceeding the fixing force produced by the magnetic force of the magnet 8 and the magnetic substance 9 is applied to the torch main unit 1, to prevent the machining head section from being broken by the impulsive force, the magnet 8 and the magnetic substance 9 are detached, the upper face of the flange 4 in an opposite direction to the portion with which the obstacle comes in contact presses an elastic member 12, and the flange 4 lifts up from the groove 3 of the bracket 2 and is detached.
As for the torch main unit 1 having the flange 4 once detached from the groove 3 as described above, after avoidance from the obstacle or removal of the obstacle, the flange 4 is pressed by the elastic member 12 and is again fitted into the groove 3 and they are magnetically fixed by the magnet 8 and the magnetic substance 9 and the torch main unit 1 is restored to the former state.
In fact, however, after the flange 4 is detached from the original fit state and a part of the flange 4 lifts up, the flange 4 may be caught in a state in which it runs on an upper margin face 2a of the bracket 2 and there is a problem of not performing smooth restoration operation. If a fit gap is made large so as to prevent the flange 4 and the upper margin face 2a from being caught in, there is a problem of degrading the centering accuracy.
In recent years, in the laser beam machine, speeding up and high acceleration of the machining operation have been going to move with performance improvement of the laser beam machine. With a three-dimensional laser beam machine, a nozzle is rotated not only downward, but also usually horizontally. The fixing force of a magnet, etc., needs to be made large so that the torch main unit 1 having a large mass and the tip nozzle part 7 are not placed out of position with a move (particularly acceleration) at the machining time. On the other hand, if the fixing force is made excessively strong, a shock cannot sufficiently be absorbed at the collision time with an obstacle and the tip nozzle part 7 may be often broken by the impulsive force before the torch main unit 1 is inclined. Focusing attention on this point, the fixing force cannot be set much strong; this is a problem.
The invention is intended for solving the problems described above and it is an object of the invention to provide a laser beam machining head wherein according to a simple structure, a breakage prevention function reliably operates for preventing damage to a machining head section and the machining head section once placed out of engagement can be reliably restored to the former engagement state.
According to the invention, there is provided a laser beam machining head comprising a first machining head section having a flange in a first end part in a direction along an optical axis direction of laser light and having a laser light emission nozzle in a second end part, a second machining head section having an engaged part engaged with the above-mentioned flange of the first machining head section for detachably holding the above-mentioned first machining head section, and an O ring being engaged in an engagement part placed in an outer peripheral surface of the above-mentioned flange opposed to an inner peripheral surface of the above-mentioned engaged part and pressed against the inner peripheral surface of the above-mentioned engaged part.
According to the above-described structure, the breakage prevention function reliably operates for preventing damage to the machining head section and the machining head section once placed out of engagement can be reliably restored to the former engagement state.
According to the invention, the laser beam machining head wherein the engaged part is formed with a tapered part is provided.
According to the above-described structure, the machining head section is restored to the former engagement state more reliably and smoothly.